Mutations

Question 1

What is a gene mutation?

Answer 1

A gene mutation is a mutation that occurs within one gene; change in DNA sequence is only seen in one gene.

Question 2

What is a chromosome mutation?

Answer 2

A chromosome mutation alters more than one gene.

Chromosome mutations can affect large portions of a chromosome, entire chromosomes or even entire sets of chromosomes.

Question 3

What are the two big categories of chromosomal mutations?

Answer 3

1. Chromosome rearrangements

2. Changes in # of chromosomes

Question 4

What are the two big categories of chromosomal mutations?

1. Chromosome rearrangements

Name the kinds of chromosome rearrangements.

Answer 4

1. Chromosome rearrangements

deletions
duplications
inversions
translocations
transpositions

(DDITT)

Question 5

Chromosome rearrangements

Answer 5

Chromosome rearrangements change the order of DNA sequences within one or more chromosomes for MORE THAN ONE gene

Question 6

What are sources of chromosomal rearrangements?

Answer 6

• double strand breaking along DNA molecule of the chromosome (usually there are at least TWO double strand breaks)

Question 7

What can cause the double strand of DNA to break?

Answer 7

High-energy radiation (X-rays or gamma rays)

• naturally produced breaks in double strand that do not get repaired
• certain chemicals biding to DNA

Question 8

True or False: Errors during meiosis in the homologous chromosome pairing and reciprocal genetic exchange can also create chromosome rearrangements.

Answer 8

True - Errors during meiosis in the homologous chromosome pairing and reciprocal genetic exchange can also create chromosome rearrangements.

Question 9

The three main mechanisms of generating chromosome rearrangements:

Answer 9

• DNA damage that creates two or more double strand breaks in DNA (that are fixed but in a way that creates new gene orders)
• errors during meiosis
• individuals that have chromosome rearrangement mutations are prone to creating even more rearrangements in their offspring

Question 10

Chromosomal rearrangements may lead to abnormal gene function and mutant phenotypes.

What are the three reasons why this might happen?

Answer 10

1. gene dosage effect - genetic imbalance between two or more genes that must work together (i.e harmful effects of having too many or two few copies of genes)
2. gene disruption - when chromosome break disrupts proper DNA sequence within a gene, destroying gene’s ability to function
3. position affect - gene is put in a chromosome location that impacts its proper functioning

Question 11

Give an example of position affect.

Answer 11

A gene is moved from euchromatic region to a heterochromatic region (transcription is inhibited)

A gene is moved closed to an enhancer elements (increase rate of transcription)

*Opposite way around possible too